A social network is a social structure made up of individuals, groups or organizations, which have been referred to as “nodes,” that are tied (connected) by one or more specific types of interdependency. For example, one or more of friendship, business associations, common interest or history, occupation, education, finances, likes/dislikes, or other relationships can connect nodes. In a simple form, a social network is a structure of these connections between nodes. The nodes to which an individual is connected represent the contacts of that individual, and the return or value than an individual derives from the social network can be measured as social capital.
A social network diagram includes nodes as points and lines representing ties or connections between the nodes. Attention given to network theory, i.e., the creation, maintenance, and destruction of such ties, has increased in recent years. The rise in such interest may be attributed to the study of internet connections, and awareness of the roles which social networks play in people's work habits, health, entertainment interests, and many other facets of daily life.
An example of a social networking and microblogging service is TWITTER, enabling its users to send and read messages called “tweets”. Tweets are text-based posts displayed on a user's profile page. TWITTER and other social messaging services would be more useful if such systems could optimize the number and nature of message recipients.